Process for preparation of poly(perchloromethyl) benzenes



Oct. 22, l1957` o. D. lvlNs ETAL PROCESS FOR PREPARATION OF POLY(PERCIlI .OROMETHYL)BENZENES Filed Aug. 20. 1954 INVENTORS Owen 0. /v/'ns E @www -QRS km wwkbm.

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James D, /eaal BY Edgar C. r/'f'fon MMM MC/ Arme/VE Ks United States Patent@ vamongst;

PROCESS Foa 1 EPARArioN oF nonvnn- :Owen D. Ivins, James aD. Head, and EdgarC: Britton, Midland, Mich.,.assiguors to TherDow Chemical `Cornpany, Midland, Mich., a corporation .0f ,Delaware This invention relates to thefpneparation of :poly-(aper- .chloromethylybenzene compounds by p erchlorination of the -side chains o f Varomatic compounds of the :benzene .series wherein from two :to :three .carbon atoms .of the aromatic :nucleus .are attached to radicals oflfthe Lgroup `consisting of methyl and chloromethylradicals and the remaining carbon atoms of the aromatic nucleus vare attached to atoms of the group consisting .of hydrogen vand chlorine. it pertains particularly to l.a continuous process tf9: r.chlorinating xylene, mesitylene, pseudocumene nuclear chlorinated .derivatives thereof and derivatives .of such .compounds already partially chlorinated fin 'one .or more of the side chains, whereby Shigh yields of products Yhaving the maximum numberiof side ehainchlorine atoms are `obtainable ifrom a lnearly theoretical proportion yof chlorine. p Y

v`For simplicity, Athe fterrn- 4Ap'olymethylbenzene oompound will 'herein be 4considered p generic Vto :aromatic hydrocarbons of -the benzene series havin'g `from two Ato three methyl groups attached to -the benzene nucleus, =nuclear -chloro derivatives lof such-hydrocarbons, and .derivatives of suchcompounds wherein a hydrogen Aatoin nhas been repl-acedrby a chlorine atom in vone orrnorefof the methylgroups. 'v

Wherever `reference isi-made herein Ato a chlorinated polymethylbenzene compound, without indication of the position of the chloro-substituents lin the molecule, -it-wil'l A:be understood `that Athe side-chain derivative lis-"intended, e. g., "by pentachloro-.o-xyleneis meant ammini',ot-'pentachloro-o-xylene. Substitution inra benzene nucleus 'will be clearly indicated, egg. 'by 'names suchas 4-chloro-o- -xylene and 2-chloro-p-xylene;

The terms. perchlorination and perChIorQmethyL I are intended-to mean -the process, and `p roducof introducing, by direct reaction lwith chlorine, -into the carbon `side chains of polymethylbenzene compounds, the maxi- -mum number Vof chlorine 4atoms capable of being v'in- :troduced -into such positions by 4that process.

The theoretical Vperchlorination of a Ipolyrrlcthylbenzene compound can tbe represented by the equation;

lyvlzlere the symbol `Ar Irepresents a `benzene, nucleus lor nuclear chloro-substituted benzene nucleus .and'inV is an imeeertmm two to three. i

However, it is not .always possible `tofreplace all of the hydrogen atoms on every side-.chain by chlorine. For example, when two of the carbon side ,chains occupy adacent positions' on the benzene nucleus, as in o-xy1ene, itis known that a maximum of five lchlorine atoms can be introduced into the two adjacent groups'by direct chlorination, as represented by theequationr-f Patented Oct. 22, 1957 Similarly, with .polymethylbenzene compounds in `which are more than two nuclear .chloro substituents, it is difficult to replace all .of the side-.chain hydrogen with chlorine.

Hitherto known processes for the preparation vof polytperchloromethyl)benzene compounds from `poly- .methylbenzene compounds by reaction with `chlorine Arequire the use of alarge excess of chlorine in order to drive .the chlorination to the highest level and Vto sweep the hydrogen chloride out of the reaction mixture. Uniessrsteps are Vtaken to recover` the excess of chlorine from the hydrogen chloride vent gas, these processes are wasteful of chlorine and unduly expensive. The recovery of chlorine from admixture with hydrogen chloride is 'troublesome, .being usually carried out by scrubbing the hydrogen chloride out with water and drying thescrubbed chlorine :with concentrated sulfuric acid `before reusing it. Besides-using a wasteful proportion of chlorine, these known processes do not always `yield satisfactory products, prob- .ablybecause the chlorination conditions -most suitable for `completing the chlorination, i. e. for introducing Ythe last of the maximum number of vchlorine atoms, are not fthe most-suitable conditions for initiating "the chlorination -of ithe starting material, `the converse being true also. These'hitherto known processes often yield products :which contain an undesirable proportion of unwanted by- :products and -tarry materials.

An object of this invention is to provide a process `whereby poly(perchloromethyl)benzene compounds can be economically prepared from polymethylbenzene compounds by direct chlorination with a nearly theoretical proportion of chlorine. Y

A further object is to provide such a 4process .whereby high vyields of poly(perchloromethyl)benzene, compounds -can be obtained while avoiding the concurrent formation of -excessive proportions of by-products and tarry materials.Y

A further object is to provide such ,a process which can be Vcarried out continuously and on a commercial scale;

A particular object is to provide such Aa method for the preparation of pentachloro-o-xylene, hexachloro-mxylene, and hexachloro-p-xylene from o-xylene, m-xylene, -p-xylene, and their partial side-chain-chlorinated deriva- `tives, respectively.

Other objects and advantages of the invention will be evident from the following description. Y

The objects of this invention are attained in a process wherein a polymethylbenzene compound in the liquid phase and chlorine are fed in countercurrent through a plurality of discrete reaction zones in series while being maintained at a reaction temperature and exposed to actinic light.

The drawing is a flow-sheet of the process and a diagrammatic representation of a suitable way for practicing the invention. p

In the present method, a polymethylbenzene compound is converted to a perchlorinated compound by reaction with a nearly theoretical proportion of chlorine, without the inconvenient recovery of an excess of unused chlorine andwithout appreciable formation of by-products and tats.

As is evident from the drawing, the present invention comprises the features of a countercurrent, multi-stage chlorination process, in which the operations can be carried on in continuous member. It is necessary to employ a plurality of distinct, discrete reaction zones, of which there should be at least-three and preferably tive, as shown in the drawing, or more. No particular limitation need be placed on the kind of apparatus used to provide these reaction zones, except that provision be made for (l) admitting a liquid feed and a gaseous feed to each zone, (2) contacting the liquid and gas phases in each Zone, (3) passing a portion of the liquid phase and a portion of the gaseous phase out of each Zone in opposite directions to the next successive reaction zones, respectively, (4) preventing each phase in each zone from returning to the zone from whence it carne, maintaining a desired temperature in each reaction zone, and (6) irradiating the liquid phase in each reaction zone with actinic light. These conditions are easily atatined by means of a series of separate vessels inter-connected to permit liquid flow in one direction and gas ow in opposite direction, from one vessel to the next in the series. Usually, a series of reactors is assembled in a cascade arrangement, with the starting liquid material being fed into the uppermost reactor and flowing downward, e. g. by gravity, to and through the successive lower reactors to the lowest reactor. Countercurrently, a gas stream is caused to ow upward from the lowest to the highest reactor, usually under pressure of chlorine fed to the lowest reactor. The plurality of reaction zones can be provided within a single structure which is subdivided into chambers with the necessary conduits for liquid and gas flow. For example, a device similar to a bubble-cap distillation column can be employed.

It is not necessary that all of the reactors in a series for practice of this invention be of the same size nor that the same amount of the reactants be in each of these .reaction zones. It is sometimes preferred that certain of the reactors be large and others small relative to each other in the apparatus.

From the reaction zone to which the polymethylbenzene compound is initially fed, to the last zone from which the poly( perchloromethyl)benzene compound product is withdrawn, there is a progressively increasing degree of chlorination of the material in the liquid phase. Ordinarily there is also a progressively increasing diiculty of further chlorination of that material in the liquid phase. It is an important feature of the present invention that the concentration of chlorine in the gas phase also progressively increases from one reaction zone to another as the degree of chlorination of the material in the liquid phase increases. Conversely, the initial starting material is chlorinated with a chlorine-containing gas which is diluted with hydrogen chloride. Among the important consequences of this process are these:

1) The initial starting material is chlorinated with a dilute chlorine which, while active enough to chlorinate the more reactive positions on the polymethylbenzene compounds, is not so active that unwanted by-products and decomposition reactions are caused to occur.

(2) The last stages of chlorination to a highly chlorinated end-product are effected by a concentrated chlorine which is suiciently reactive to drive the reaction quickly to completion and is not handicapped by dilution with an appreciable proportion of hydrogen chloride.

(3) Overall, only a theoretical proportion of chlorine is required.

(4) In the continuous process, the operation in each reaction zone can be maintained at substantially constant and optimum conditions, and excellent control of the process can be readily obtained.

(5) A high production rate can be maintained with a minimum of inventory of materials in process and a rela? tively short reaction time, thereby further minimizing by; product formation, increasing the quality ofthe product and reducing the hazards of the operation.

The economical consumption of chlorine is of considerable importance since it has not hitherfore been thought possible to prepare a poly(perchloromethyl)benzene compound, such as pentachloro-o-xylene, unless a large ex-v cess, e. g. a 3- to S-fold excess, of chlorine were employed.

Usually, in practice of this invention, a polymethyl-V benzene compound in liquid form is fed continuously into one of the end reaction zones and chlorine gas is fed into the other end zone of a series of reaction zones as herein described. The relative rates of feed of the polymethylbenzene compound and of chlorine correspond closely to those theoretically required for production of the corresponding poly(perchloromethyl)benzene compound. For example, in the preparation of pentachloro-o-xylene, approximately ve moles of chlorine are fed per mole of o-xylene; in the preparation of hexachloro-p-xylene, approximately six moles of chlorine are fed per mole of p-xylene. The liquid phase is caused to move through the series of zones toward the chlorine inlet end while the gas phase is caused to flow oppositely toward the organic feed inlet end of the series of zones. The liquid phase is irradiated with actinic light, preferably radiations rich in the violet and ultra-violet region of the spectrum. It is important that the radiation be confined principally to the liquid phase in order to cause the reaction to occur in the liquid phase and not in the vapor phase.

During passage through the respective reaction zones, the liquid and gas phases are thoroughly contacted. Usually, bubbling the gas through the liquid by means of a gas sparger provides sufficient mixing, but mechanical stirrers, batlles or packing materials can be employed. The reaction zones can contain such heating or cooling devices as are necessary to maintain the reaction mixture at a chosen temperature, or these devices can be employed on the liquid conduits between reaction zones. Usually, in the zones where the lirst chlorination of the polymethylbenzene compound occurs, cooling is required to remove heat of reaction. In the latter zones, where the perchlorination is completed, it is usually necessary to Asupply heat to maintain the liquid at reaction temperatures.

The most desirable reaction temperature to be maintained in the reaction vzones depends on the particular material being chlorinated and product being made, and is usually between about and about 160 C. In the case of the preparation of pentachloro-o-xylene from o-xylene, the preferred reaction temperature range is from `about 90 to about 115 C. in order to avoid the occurrence of chlorinolysis, i. e., the cleavage of side chain carbon groups from the benzene nucleus which sometimes occurs with o-xylene derivatives at higher temperatures. In some instances, it is desirable to maintain' certain of the discrete reaction zones at temperatures different from those of others, e. g. higher temperatures in zones of higher chlorine content.

The process is usually carried out at atmospheric pressure, although pressures above or below atmospheric pressure can be used. Y

The liquid eluent from lthe last zone, i. e., the zone of entry of chlorine into the process, usually contains some dissolved chlorine which can be removed by usual means, e. g. by blowing with an inert gas such as air, nitrogen, carbon dioxide or the like in a conventional scrubber as shown in the drawing. Alternatively, chlorine and acid impurities can be removed from the poly- (perchloromethyl)benzene product by chemical means or by washing with Water. There is thereby obtained a perchlorinated polymethylbenzene compound product 'substantially free of unreacted chlorine. The scrubbing gas, if one be used, can be fed to one of the early reacition zones, e. g., the zone into which the organic startfing'materialis fed, to utilize the chlorine purged from -the perchlorinated product.

The vapor efllueut from the first reaction zone is substantially free of chlorine. After cooling, whereby most of the organicvapors are condensed and returned to the reaction system, the gas is preferably scrubbed with Water in a conventional scrubber, whereby the hydrogen chloride is dissolved, forming hydrochloric acid, and the remaining organic vapors are condensed. The vent gases from thephydrochloric acidscrubber consist largely of the inert gas from the perchlorinated product scrubber. From the hydrochloric acid scrubber, the organic mate asia-eos i rial can be separated, dried and recovered ffor return t9 .the prooess The -hydroohlorio heid ogn he utili'zedelsewhere or discarded. The hydrogen chloride can be conyerted to ehlorne, e, ghy oxidation, and the `ohlerine returned to the process. Y t

The present method is particularly advantageous for the perchlorination of diand tri-methylbenzene compounds and especiallyvof o-xylene, rrr-xylene, p-xylene, t

i Mixtures of polyrnethylbenzene ompoundsjcan also be used as starting materials, and commercial compositions, Containing iootnerie and homologous compounds and impurities normally assoiatedwith their'origin, are generally suitable. For example, commercial xylene, being a mixture of isomeric xylenes and usually containing ethylbenzene, toluene, some `trimethylbenzenes, ethyltoluene and aliphatic hydrocarbons boiling in the xylene boiling range, can be-employed in this process toy obtain ri:inttttr o fpoly(perohloornethyl)benhenes.

Materials already partially chlorinated in the -methyl .groups een he usen es Starting materiels when these aie f :iyailable.y Often it is advantageous totprepare a par,- tially chlorinated material by a.` preliminary'batch reac.- ,Stepr thereby furnishing n ntoredesirnhlefeed nieterial forl the continuous process of this invention, -Eor example, a xylene, or mixtures of xylenes, can be chlo rinated eciently with up toV about twotrnoleculargpro- .portions of chlorine, e." g., to Vform a'rdichlnroxylene product, in an ordinary batch processinthe wellflnown manner. The resulting" partially chlorinated material, comprising ic-chloroxyle'ne's, o;,atidichlordxylenesi` and `the like, is suitable for use as starting material in the present continuous process. Such a material is especially edi/antagonistas. n starting tnntetinl heonueefduejto its l der vaporpressure as 4compa;ed to the corresponding hydrocarbons, a lesser amount of organic material is swept out of the iirst reactor with the hydrogen chloride gas stream. Furthermore, the volume. of that hydrogen chlorideV gas stream is itself `lessened because of Vthe lesser amount of chlorination required by the already partially chlorinated feed material.

Usually, the starting material, 1n a liquid f orm, is used Without added solvent, butusual chlorination solyents can be used and are preferably used when the `starting material is otherwise diiiicult to liquefy.

The following examples illustrate ways in which the invention has been practiced, but should notbecon- Vstrued as limiting its scope.

hXnMgLaRYAPPARATUs AND MODE op oPngAnoN A multi-stage, cOunteIcurrent, continuous chlorination apparatus, of which the drawing is a diagrammatic representation, was assembled as follows:

A group of five 2-liter glass reaction aslrcs was arranged and interconnected in step-down or series cascade fashion, one being vnt a highest elevation, the nent at a lowerlevel, the nextat a still lower level Vand so on to the last at a lowest level.Y For convenience, the reactor at highest level is herein referred to as the first reactor an@ the. nunthering ie ,eontinueu etonseoutively to the reactor at lowest level as the cr last reaV or, from .eheh reactor, except .the last, a conduit was provided for passing liquid to the next lower reaotOr, .each re.- actor being maintained about half-full of liquid during operation Aof the process. From each reactor, except the first, `a cenduit was provided'lfor passing gas to, and beneath the liquid in, the Vnext higher reactor. To .the

:inst '.reaetotla .liauis polytnethylhenzene stattingrnntetinl "was vfed froma storage vessel through flow-control valves.

Fiom the first renotor, Vthe gases Vwere 'passed' upward., through a reuxgcondensenghence to the 4bottom-cfa scrubber consisting of a packed column down which flowed a stream `of water. Top gases from the scrubber were vented to Waste. The bottom liquid eluent from the scrubber 4was cooled and separated in a mechanical separatornwhereby a hydrochloric acid product and a recovered organic material were obtained.

To the last renotor, ohlotine gas was bubble@ beneath the" liquid charge. The chlorine gas was obtained from n storage cylinder antl'nhssed through tho'usual. train of traps, scrubbers, safety reliefdevice and flow/meter". From the last reacton'the liquid product passed tothe top of a scrubber column and flowed downward against a strega! onitrogen gne passed into the hettotnof the scrubber, The ,topivapors from this Vscrubber contained Chlorine gas and were .passed` to the firstgreactor and huhhieti heneeth the liquid therein- The liquid protiuet from the nitrogen scrubber was taken as the p,lyi(per ehiotoinethylhenzene produet- Eheh renotor contnined nV thermoeouple for determina Y,tion or temperature therein and provision was lmade for heating or cooling the contents of each reactor to maintain those contents within n desired Yrenetion temperature RuigeY Through the glass bottom o f eheh reactor, he liquid therein was illuminated hy .light from a .type RS, 275-Wnttsun1n1np, Whieh produeed an appreciable .amount Of ,radiation inthe region below 480.0 Angstrom units.

i Example; i This example illustrates the preparation of pentachloroo-xylene' from o-xylene.

To `the @r-stgreactorofV the apparatus just described WnS fed ovni/iene gt. an. layering; i o li35, granislner hour While chlorine V-was gfedgintoethe last reactolEV at an average rate of lpound V(2153.6 grams) per h'o'ur.V The temperature of the first reactor was maintained at SOP-99 C. while the temperatures in the other reactors 2-5 were maintained at about l115 C. After the process lhad been operated for a time long enough to attain a steady state, a sample of liquid reaction mixture was taken` from each reactor and analyzed. Table l shows the composition, in percent by Weight, of the organic material in each reactor zone under the conditions just described..

TABLE I Reactor No Q 1 2 3 4 5Y o-Xyleue -Q 35 Monochloro-o-xylene. Dichloro-oxylene Trichloro-o-xylene..- Tetrachloro-o-xylene Pentachloro-o-xylene Both the hydrogen chloride gas from the iirst reactor and the pentachloro-o-xylene product from the nitrogen scrubber were substantially free of unreacted chlorine.

Exemple 2 of hexachloroa2,810,6`se

Temperature Reactor No. Range, C.

After two days of operation, the liquid in each reactor was sampled and analyzed as follows:

Hexaehloro-pxylene, percent Reactor No.

. by Weight nil. less than 5.

blik

During the next 43 hours of operation, 5820 grams of p-xylene and 22,930 grams of chlorine were used under the conditions hereinbefore described. During this portion of the test, about 279 grams of p-xylene was recovered from the vhydrochloric acid separator while 15,485 grams of hexachloro-p-xylene was collected from the nitrogen scrubber. Based on the p-xylene consumed, the recovery of hexachloro-p-xylene is 94.7 percent of theory and is 92 percent of theoretical based on chlorine used. Ninety-two percent of the chlorine was also accounted for as hydrochloric acid from the gas scrubber.

At the conclusion of the test, the liquid in the reactors was again sampled and analyzed as follows:

Hexachloro-pxylene, Percent by Weight Reactor No.

not tested.

tinuous perchlorination of p-xylene by the method of this invention, p-xylene was chlorinated by a batch procedure. To 7 grams-moles of p-xylene at a temperature of 60 C. was added chlorine gas. The temperature of the mixture rose spontaneously and was allowed to increase to 130f-1407 C. whereupon cooling was applied and the temperature thereafter was held between 140 and 150 C. while a total of 56 gram-moles of chlorine (14 grammoles more than theoretically required) was bubbled Yinto the liquid mixture over a period of 21.5 hours. Dur- .ing the last portion of the chlorination, an increasing proportion of chlorine passed through the reaction mixture without being reacted and was lost by venting with the hydrogen chloride. The crude chlorinated p-xylene product melted at a temperature of 87-105 C., corresponding to a composition of approximately 80-85% hexachloro-p-xylene by weight. Thus, the batch chlorination Was obviously not complete, in spite of the excess of chlorine which had been employed. Furthermore, the product was colored a dark brown with tarry byproducts of side reactions.

In place of the o-xylene and p-xylene used as starting materials in the foregoing examples, there can be substituted another polymethylbenzene compound or mixtures thereof, such as commercial xylene which is a .mixture of isomeric xylenes and other close-boiling hydroa A, carbons. Also, nuclear chloropolymethylbenzene compounds and materials already partially chlorinated in the carbon side chains, such as a-chloroxylene and oued-dichloroxylene, can be employed with substantially similar results.

Example 3 This example illustrates the perchlorination of a commercial mixture of xylenes having the following analysis by weight.

y Percent o-Xylene 1 m-Xylene 60 p-Xylene 22 Toluene 2 Ethylbenzene 15 The commercial xylene mixture had been distilled to remove water and traces of iron. i

The xylene mixture was fed at rates of from 200 to 210 mls. per hour to the first vessel of the continuous chlorination apparatus hereinbefore described, in countercurrent to chlorine fed into the vast vessel of the series at an average rate of 1.5 pounds per hour. Temperatures in the several vessels were maintained in the following ranges during three days duration of the run:

No. 1 at 90-100 C. N0. 2 at 120-130 C. NOS. 3-5 at 140-150 C.

` Percent Pentachloro-o-xylene 1 Hexachloro-m-xylene 44 Heptachloro-m-xylene (note) 15 Hexachloro-p-xylene 22 Benzotrichloride 2 Pentachloroethylbenzene 14 NOTE- The formation of some heptachloro-m-xylene is probably the consequence of nuclear chlorination of m-xylene wliclh t'occurs very readily, even in the absence of added ca a ys s.

Example 4 This example illustrates the preparation of aliphaticoctachloropseudocumene.

In an apparatus, and by a procedure, similar to that hereinbefore described, pseudocumene was fed to the rst reactor at an average rate of about ccs. per hour while feeding one pound (453.6 grams) of chlorine per hour to the last reactor. The temperatures in the ve reactor vessels were maintained progressively higher from 60-80 C. in the rst vessel to 140-150 C. in the last vessel. The chlorinated pseudocumene product was passed through the nitrogen scrubber and emerged substantially free of unreacted chlorine. The vent gas from the first reactor was also substantially free of unreacted chlorine.

Analysis of the perchlorinated pseudocumene product showed 70.6 percent by weight chlorine, corresponding to an average of about eight chlorine atoms per molecule. The product was a mixture, probably consisting predominately of a,,a',2,a2,a4,a4,@t4-octachloropseudocumene and ,a,ot2,a2,0t2,a4,a4,a4 octachloropseudocumene.

Example 5 This example illustrates the perchlorination of p-xylene on a semi-commercial scale.

"9 f A continuouschlorination "plant 'twee onstgucred on the same principles as were embodied in the laboratory apparatus hereinbefore .li'scribedf Fille GhiQIiDaliOn fe- -actors were arrayed in series on .yediicront ,levels talla .numbered v1-5 from top downward. Each .reeotor Vwas essentially a cylinder 115 inches in zdiametor by LSinQhe-,S `in length having its major axis'herizontal. The reactors were interconnected with conduits for fOW of liquid lQllt `of each reactor from va'point near .the topzof the reactor down to the next lower reactonlexcept that the liquid from the lowest reactor (Number 5=) -owed to a -gas scrubber. In operation, .each reactor containedabout 11 `gallons of liquid. Conduits were also provided at the top of each reactor for ow of gas fromeaoh .reactor upward into the next higher reactor, except that the gas from the top (Number 41) reactor `passed through a reliux condenser to a lwater scrubber for absorption of hydrogen chloride. The gas conduits Pled to .perforated pipe gas `spargers near the bottom of the vessels. Chlo- Aripe gas was fed `to the lowest (Number y5)k reactor through the .usual gas train devices,

Each reactor was equipped Vwith a Pyrex glass well in which was a 1200 watt, type UA11 photochemical lamp emitting about 22 percent of its energy in the form of light having wavelengths in the range from about 2200 to about 5400 Angstrom units, the entire wellbeing below the liquid level in the reactor during operation.

The reactors were also equipped with internal pipe coils for heating or cooling the contents of the reactors by indirect Contact with fluid heat transfer media such as steam or water. A11 of the conduits for gas -or liquid reaction materials were jacketed for passage of heat transfer media. The apparatus was also equipped with the usual appurtenances such as valves, pressure gauges, safety devices, dow-meters, temperature recorders, and the like for the control of the operation.

In operation of this plant for the preparation of a,a,a,u,a,a hexachloro p xylene, liquid p Xylene, (97 percent by weight assay, the balance being orthoand meta-Xylene and toluene) was fed into the first chlorinator, i. e., the top-most reactor, at an average rate of 11.2 pounds per hour.

Chlorine gas was fed into the last chlorinator, i. e., the bottom-most reactor, at an average of about 42 pounds per hour.

The temperature in the reflux condenser was held at -25 C. and temperatures in the chlorinators were held in the following ranges:

Number 1 C 75-80 Numbers 2-5 C 130-140 The hydrogen chloride vent gas was substantially free of unreaced chlorine, but contained some Xylene vaporized and swept out of the irst chlorinator. This Xylene was recovered but was not returned directly to the process. Instead, the rate of feed of fresh p-xylene was made to compensate for the proportion of xylene removed from the system by the exit gas stream, the net proportion of p-Xylene retained by the system being approximately one mole per six moles of chlorine fed.

The perchlorinated product from the last chlorinator was passed through a nitrogen gas scrubber, the vent gas from the scrubber being admixed with the gasstream ilowing into the second chlorinator. The hexachlorop-xylene product emerged from the nitrogen scrubber at an average rate of about 3l pounds per hour, substantially free of unreacted chlorine.

We claim:

1. A process for making poly(perchloromethyl)benzene compounds which comprises passing, in intimate contact and in countercurrent through a plurality of discrete reaction zones in series, a gas stream comprising chlorine and a liquid stream comprising at least one aromatic compound of the benzene series wherein 10 rrom'two to thro@ carbon atoms of the aromatic nucleus are attached to :radicals ,St-.looted from the group consistirlgof methyl and ohlotomottlyl radicals and the remaining carbon atoms ofthe aromatic nucleus are attached to atoms selected from the group consisting of hydrogen .and chlorine` atoms, establishing in each such discrete reaction zone a liquid phase consisting Substantially of `the constituents of the liquid stream and containing constituents of the gas ,stream dispersed therein anda gas -phase consisting substantially of the constituents of the gas lstream together with any constituents vaporized 'from the liquid stream, maintaining the liquid Phase io .each reaction .zone ata temperature .conducive to chlorinationof the aromatic compound, and irradaug th.e liquid phase in each discrete Vreaction zone with actinic radiation ina manner $11.611 as IQ 6.9115114- lll? f fdiill vsubstantially .toV the liquid phase while preventing appreciable irradiating of the gas phase in such zone,

2. A process for making poly(perchloromethyl)benzene compounds, which process comprises. fedlllg gas `to one end, and a liquid to .the `other end, vof a series of atleast three .discrete .and interconnected reaction 2.09.65, the gas comprising chlorine and the liquid comprising at least one aromatic compound of the benzene series wherein from two to three carbon atoms of the aromatic nucleus are attached to carbon side chains selected from the group consisting of methyl and chloromethyl radicals and the remaining carbon atoms of the aromatic nucleus are attached to atoms selected from the group consisting of hydrogen and chlorine atomsthe gas and liquid being fed at rates such that the chlorine in the chlorine-containing gas corresponds approximately to the proportionv of chlorine required to perchlorinate the carbon side chains of the aromatic compound in the liquid, thereby forming a gas stream comprising chlorine and a liquid stream comprising the aromatic compound, passing the gas stream and the liquid stream in intimate contact and countercurrent ilow through the series of discrete reaction zones, establishing in each discrete reaction zone a liquid phase consisting substantially of the constituents of the liquid stream and containing constituents of the gas stream dispersed therein and a gas phase consistingV substantially of the constituents of the gas stream together with any constituents vaporized from the liquid stream, maintaining the liquid phase in each reaction zone at a temperature conducive to chlorination of the aromatic compound, and irradiating the liquid phase in each discrete reaction zone with actinic radiation in a manner such as to conline the radiations substantially to the liquid phase while preventing appreciable irradiating of the gas phase in such zone.

3. A process according to claim 2 wherein the chlorination reaction temperature is in the range from to 160 C., said range being from 90 to 115 C. when the aromatic compound is an o-Xylene compound.

4. A process for making bis-(perchloromethyl)-benzenes according to claim 3 wherein the aromatic compound of the ybenzene series is at least one xylene.

5. A continuous process for making bis-(perchloromethyl)benzenes from aromatic compounds of the benzene series wherein two carbon atoms of the aromatic nucleus are attached to carbon side chains selected from the group consisting of methyl and chloromethyl radicals and the remaining carbon atoms of the aromatic nucleus are attached to hydrogen atoms, which process comprises feeding at least one such aromatic compound in a liquid form into the first reaction vessel of a series of at least three interconnected reaction vessels and feeding chlorine gas into the last reaction vessel of such series, the relative rates of feeding chlorine and the aromatic compound being such as to correspond approximately to the proportion of chlorine necessary to perchlorinate the carbon side chains-of the aromatic compound, forming in each reaction vessel a reaction mixture comprising liquid constituents and gas constituents, establishing in each re- 11 action vessel a liquid phase consisting substantially of the liquid constituents and containing a portion of the gas constituents dispersed therein and a gas phase consisting substantially of the gas constituents together with any vaporized liquid constituents, feeding the starting chlorine gas into intimate contact with the liquid phase in the last reaction vessel of the series, passinga portion of the gas phase from each reaction vessel except the rst vessel into intimate contact with the liquid phase in the next preceding vessel of the series, passing a portion of the liquid phase from each reaction vessel eX- cept the last vessel into the next succeeding vessel of the series, maintaining the liquid phase in each reaction vessel at a temperature in the range from 90 to 160 C., said range being from 90 to 115 C. when the starting aromatic compound is an lo-Xylene compound, irradiating the liquid phase in each reaction vessel with actinic radiation in a manner such as to conne the radiation substantially to the liquid phase while preventing appreciable irradiating of the gas phase in such reaction 20 vessel, withdrawing a portion of the liquid phase from the last reaction vessel in the series and venting a portion `vessels except the last reaction vessel.

7. A continuous process for making a,a,a,a,penta chloro-o-Xylene according to claim 5, wherein the aromatic compound is o-Xylene.

8. A continuous process for making a,a,a,a',a',ahexa chloro-p-xylene according to claim 5, wherein the aromatic compound is p-xylene.

References Cited in the le of this patent UNITED STATES PATENTS 1,828,858 Conklin Oct. 27, 1931 2,132,361 Osswald et al. Oct. 4, 1938 2,608,660 Noebels Aug. 26, 1952 2,695,873 Loverde Nov. 30, 1954 

1. A PROCESS FOR MAKING POLY(PERCHLOROMETHYL) BENZENE COMPOUNDS WHICH COMPRISES PASSING, IN INTIMATE CONTACT AND IN COUNTERCURRENT THROUGH A PLURALITY OF DISCRETE REACTION ZONES IN SERIES, A GAS STREAM COMPPRISING CHLORINE AND A LIQUID STREAM COMPRISING AT LEAST ONE AROMATIC COMPOUND OF THE BENZENE SERIES WHEREIN FROM TWO TO THREE CARBON ATOMS OF THE AROMATIC NUCLEUS ARE ATTACHED TO RADICALS SELECTED FROM THE GROUP CONSISTING OF METHYL AND CHLOROMETHYL RADICALS AND THE REMAINING CARBON ATOMS OF THE AROMATIC NUCLEUS ARE ATTACHED TO ATOMS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND CHLORINE ATOMS, ESTABLISHING IN EACH SUCH DISCRETE REACTION ZONE A LIQUID PHASE CONSISTING SUBSTANTIALLY OF THE CONSITUTENTS TO THE LIQUID STREAM AND CONTAINING CONSTITUENTS OF THE GAS STREAM DISPERSED THEREIN AND A GAS PHASE CONSISTING OF THE LIQUID STREAM AND CONTAINING CONGAS STREAM TOGETHER WITH ANY CONSITITUENTS VAPORIZED FROM THE LIQUID STREAM, MAINTAINING THE LIQUID PHASE IN EACH REACTION ZONE AT A TEMPERATURE CONDUCIVE TO CHLORINATION OF THE ARMATIC COMPOUND, AND IRRADIATING THE LIQUID PHASE IN EACH DISCREATE REACTION ZONE WITH ACTING RADIATION IN A MANNER SUCH AS TO CONFINE THE RADIATION SUBSTANTIALLY TO THE LIQUID PHASE WHILE PREVENTING APPRECIABLE IRRADIATING OF THE GAS PHASE IN SUCH ZONE. 